Constant speed control means for variable pitch propellers



E; H. HARTEL Aug. 10, 1954 CONSTANT SPEED CONTROL MEANS FOR VARIABLEPITCH PROPELLERS Filed Jan. 6, 1949 '7 Sheets-Sheet l R m W W.

Aug. 10, 1954 Filed Jan. 6, 1949 E. H. HARTEL CONSTANT SPEED CONTROLMEANS FOR VARIABLE PITCH PROPELLERS '7 Sheets-Sheet 2 Aug. '10, 1954 E.H. HARTEL- 2,585,932

CONSTANT SPEED CONTROL. MEANS FOR VARIABLE PITCH 'PROPELLERS Filed Jan.6, 1949 7 Sheefs-Sheet a if l/ II III 11 I IIIIIIIIIIILIIIU J; an s IRPL] H I h 'H /l n UH TH //l R l Q I INVENTOR.

E. H. HARTEL Aug. 10, 1954 CONSTANT SPEED CONTROL MEANS FOR VARIABLEPITCH PROPELLERS Filed Jan. 6, 1949 7 Sheets-Sheet 4 QQQE T115- 7 Fix 3.5

M ll/VENTOR. "M

E. H. HARTEL 2,685,932

CONSTANT SPEED CONTROL MEANS FOR VARIABLE PITCH PROPELLERS Aug. 10, 19547 Sheets-Sheet 5 Filed Jan. 6, 1949 II ill-ril- WWW A g- 1954 E. H.HARTEL 2,685,932

CONSTANT SPEED CONTROL MEANS FOR VARIABLE PITCH PROPELLERS '7Shelets-Sheet 6 Filed Jan. 6, 1949 M INVENTOR. W

10, 1954 E. H. HARTEL 2,685,932

CONSTANT SPEED CONTROL MEANS FOR VARIABLE PITCH PROPELLERS Filed Jan. 6,1949 7 Sheets-Sheet '7 IN V ENTOR.

Patented Aug. 10, 1954 CONSTANT SPEED CONTROL MEANS FOR VARIABLE PITCHPROPELLERS ErwinH. Hartel, Cleveland, Ohio Application January 6, 1949,Serial No. 69,471

27 Claims. 1

This application is a continuation in part of my co-pending application,Serial No. 35,143, filed June 25, 1948, now abandoned, for ConstantSpeed Control Means for Variable Pitch Propellers.

This invention appertains to speed control means, and more particularlyto control means for maintaining constant speed of the rotating member,especially adapted in the art of aircraft for maintaining constant speedof a variable pitch propeller.

An engine driving a propeller should preferably operate uniformly sothat the propeller driving shaft rotates at a constant or uniform speedfor which it is especially designed, under usual conditions, asordinarily that is the speed at which the engine operates mostefliciently. In order to maintain the propeller rotating at a constantspeed it is necessary to vary the pitch of the propeller blades inaccordance with vary ing conditions of difierent air speeds and airdensity.

The energy absorbed by a rotating propeller having radial blades dependslargely upon the pitch of the blades and the power required by thepropeller to drive it at a given speed increases with the increase ofpitch of the propeller blades. If the pitch of the propeller bladesinitially is high at commencement of rotation, the resistance theretowill be greater and a greater load will be put upon the engine, with theconsequence that it will take a certain high plane speed for thepropeller driving shaft to reach its normal most eiiicient or constantoperating speed. It is therefore desirable that the propeller bladeshould have low pitch when starting in order that the propeller shaft ofthe engine will reach its most efficient operating or constant speed atlow plane speed. It is also desirable that when the airplane is comingin for a landing and the engine is running at relatively low speed, thepitch of the propeller blade should be low so that in the event theengine speed needs to be increased quickly for emergency power, thepropeller pitch should be at a minimum to reduce the resistance thereofto attaining high speed rapidly if the condition warrants.

When the airplane is cruising, the engine will normally be operated atits constant speed, and

it is, of course, desirable to provide for automatic variation ofpropeller pitch to maintain such constant speed of the propeller drivingshaft, such means enabling the pitch of the blades to vary in accordancewith the density of the air at flying levels of the aircraft and inaccordance with airplane speed, so that if the air density increases orthe plane speed decreases, the pitch of the propeller blades willautomatically be decreased, and if the air becomes more rarified, or theplane speed increases, the pitch of the propeller blade willautomatically be increased to meet this condition. Thus the engine willconstantly operate at its most efficient uniform or constant speed.

With the foregoing general requirements in mind, my invention aims toprovide control means for automatically controlling the pitch of theengine driven propeller blades to meet the requirements of allconditions in the operation of an airplane from starting of the enginethrough initial forward movement of the airplane, takeoff, climbing,cruising, and landing.

In its general aspects my invention aims to provide such control meanswhich takes account of the desirability of maintaining the pitch of thepropeller blades at low pitch at the time of the starting of the motor,and warming up of th motor, and until the speed of the airplane reachesa certain speed for take-01f, so that the propeller driving shaft canreach its normal most efficient or constant speed of rotation as quicklyas possible, and at low airplane speed.

My invention further takes account of the desirability of decreasing thepitch of the propeller blades to their minimum pitch as rapidly aspossible when the speed of the engine is suddenly decreased after thepropeller has been rotating at higher speed with the blades at higherpitch.

In carrying my invention into practice, I contemplate the provision of acontrol device designed to be mounted for rotation about an axisconcentric with the axis of rotation of the propeller or the drivingshaft of the latter, the provision of instrumentalities for causingrotation of said control device under the influence of air streammovement independently of the propeller; the provision of otherinstrumentalities for efiectuating direct connection of the controldevice with the propeller forcausing rotation of the two together, saidlatter devices being automatically operable for this purpose; and theprovision of instrumentalities associated with said control device andwith said propeller for changing the pitch of the propeller bladespursuant to a difierence in speed of rotation of the control device fromthe speed of rotation of the propeller.

V In accordancewith my invention, I contemplate the provision of acontrol device including a rotatable member having centrifugal elementsassociated therewith for movement radially thereof, resilient elementsopposing radial outward movement of the centrifugal elements, and van orblade elements associated with the rotatable member for rotation aboutthe respective blade axes for changing the pitch of the blade elements,and means associated with the blade elements and centrifugal elements,for rotating the blade element about its axis upon outward radialmovement or inward radial movement of the centrifugal element, forchanging the pitch of the blade elements.

In accordance with my invention, the instrumentalities forinterconnecting the control device for direct rotation with thepropeller include means operable by centrifugal force for automaticallyeifectuating direct connection between the control device and thepropeller and for causing release of said connection.

Another feature of my invention involves the provision, in connectionwith the operating instrumentalities for eifectuating propeller pitchchange when a diiference occurs between the speed of rotation of thecontrol device and the speed of rotation of the propeller, of means forabsorbing shock in said operating instrumentalities to prevent damagewhen parts of those instrumentalities reach certain limits of movement,said means effecting yieldable and resilient frictional connectionbetween said operating parts of the operating instrumentalities.

Another feature of my invention involves a special relationship betweenthe centrifugal elements and resilient elements opposing radial outwardmovement thereof, whereby, at a certain rotational speed of therotatable member carrying said elements, equality exists between theopposing forces thereof, irrespective of radial positioning of thecentrifugal elements.

Another feature of my invention involves the provision of meanscooperative with the centrifugal elements for coordinating the speed ofradial movement thereof with the rate of acceleration and decelerationof the rotatable member carrying said elements whereby to preventovercorrection of the rotational speed of the rotatable member.

Still another feature of my invention involves the provision of mean fordampening the radial movement of the centrifugal elements relative tothe rotatable member, said means utilizing lubrieating oil as thedampening medium whereby to lubricate the centrifugal elements andassociated mechanism.

In the drawings:

Figure 1 is a view showing a propeller mechanism embodying my invention,the said view showing a propeller head, including the propeller bladesand the pitch changing mechanism, mounted on the forward end of thepropeller drive shaft, and showing the control device mounted forrotation on an axis concentric with the propeller drive shaft in frontof the propeller, and also showing the various instrumentalitiesinterassociating said control device with said propeller head, portionsof the propeller head housing and control device housing being shownbroken away and certain parts being shown in section, about on the linesl-l of Figure 2.

Figure 2 is a section taken on the line 2-2 of Figure 1, illustratingdetails of the control device.

Figure 3 is a section taken on the line 3'% of Figure 1, and showingmore particularly details of the propeller pitch changing mechanismassociated with the propeller blades.

Figure e is a diagrammatic view of the centrifugal element andassociated yieldable or resilient element, illustrating principles ofoperation.

Figures 5 and 6- are similar views showing a portion of the controldevice including the centrifugal element and associated yieldable orresilient element, and their associated control vane, Figure 6illustrating certain of the parts in a different position from thatshown in Figure 5) these views being taken as if looking from the rearof Figure 2.

Figure 7 is a diagrammatic view illustrating the pitch of the controlvane of Figure 5, the view illustrating the vane as if the section hadbeen taken on the line 1-7 of Figure 5.

Figure 8 is a view similar to Figure '7, but illustrating the controlvane as if the section had been taken on the line 88 of Figure 6.

Figure 9 and 10 are diagrammatic views illustrating the forces acting onthe control vane at different air speeds.

Figure 11 is a graphical illustration of the characteristic curve of thepropeller during takeoff.

Figure 12 is a sectional view through a twobladed propeller illustratinga modification of my invention.

Figure 13 is a sectional view substantially on the line l3l3 of Figure12.

Figure 14 is an enlarged detail, in front elevation, of a portion of thecontrol device illustrating a modification of the invention.

Figure 15 i a sectional view substantially on the line I5-I 5 of Figure14.

Figure 16 is a detail sectional View of a portion of the structure ofFigures 14 and 15.

In Figures 1 to 11 inclusive I have shown a propeller A and controldevice B therefor, embodying my invention, said propeller and controldevice being adapted to be mounted on an airplane. 7 In these views thecontrol device 13 is carried by the propeller A which is mounted on thepropeller shaft 3 for rotation therewith. The shaft 3 is a driving shaftoperatively connected with the airplane engine (not shown) and saidshaft 3 is rotatably mounted in a bearing 3a mounted upon and forming apart of the aircraft and thus serving as supporting means for both thepropeller A and the control device B.

Now describing the invention and referring first to Figures 1, 2, and 3,the propeller mechanism there illustrated comprises the propeller headgenerally indicated by the letter A, and the control device generallyindicated by the letter 13, together with their associatedinstrumentalities which will be described. The propeller head Agenerally consists of a two-part casting 1 comprising a housing for thepropeller blade pitch changing mechanism and a hub for the propellerblade, as best seen in Figure 3. The hub portion 2 is mounted on thepropeller drive shaft 3 and suitably fixed thereto for rotationtherewith, as seen in Figure l. The propeller blades =3 and 5 aremounted on the propeller head in opposed relation, the inner ends of theblades i and 5 being received, respectively, in hub portions ii and I ofthe propeller casting l for rotation of the blades and 5 about theirrespective axes concentric with one another within the hub portions 6and l. The blades 4 and 5 are interconnected by suitable gearing, laterto be described, for effecting rotation of the blades 4 and 5 inopposite directions about their axes and in unison for changing thepitch of the blades.

The propeller head A is provided with a suitable streamlined outer shellindicated by the numeral 8.

Now referring to the control device generally indicated by the letter B,the same comprises a circular disc apertured at its center to receivethe hub iii suitably bolted thereto. The disc 9 is provided with aplurality of radial slots 1 l and ii the outer ends of which are closedby blocks or plates i2 forming bearings for the blade shafts 13 or iscarrying the blades I5 or [6 arranged alternately equidistantly radiallyof the disc 9. The shaft I l for each of the blades l6 have enlargedportions Ma disposed radially inwardly of the respective blocks orbacking plates l2 and bearing thereagainst for retaining the blades 16in proper position radially of the disc 9.

The shafts It for the blades or vanes l5 have enlarged portions 13awhich extend the full length of the slots H and the outer shoulders ofwhich bear against a block or backing plate l2, and the inner ends ofwhich bear against the disc 9 at the inner ends of the slots I l, asseen best in Figure 6. Each of the shaft portions l3a has associatedtherewith a centrifugally responsive element or weight ll having acentral bore receiving the enlarged shaft portion 13a for slidingmovement of the element ll axially thereof. Each of the centrifugalelements IT has guide grooves flat at opposite sides thereof receivingportions of the disc 9 at opposite sides of the slots H for guiding thecentrifugal elements ii in their movement radially of the disc 9 andpreventing rotation of the elements [1, relative to the disc 9. Each ofthe centrifugal elements ll has a counter-bore llb serving as a socketfor receiving the inner end of the spring [8 which encircles theenlarged portion [3a of the shaft IS, the outer end of which springbears against the backing plate 12. The springs W are designed toyieldably resist the radial outward movement of the centrifugal elementsll due to centrifugal force during rotation of the disc 9.

Each of the shaft portions I3a has a helical groove l9 extending fromthe inner end of the shaft to a point intermediate the ends of theenlarged shaft portion [3a, each of said grooves l9 receiving arespective pin fixed to the centrifugal element ll, whereby radialmovement of the centrifugal element l1 relative to the disc 9 will causerotation of the shaft M and thereby change the pitch of the vane I5.

The blades or vanes 15 and. [6 of the control device are all, of course,in the same phase of pitch, and, in order to maintain this condition atall times the shafts of the blades or vanes l5 and it are interconnectedfor rotation in unison by the provision of a respective pinion 2!meshing with a respective toothed portion 22 of a ring gear 23 mountedfor rotation relative to the disc 9 upon rollers 2d rotatably mountedupon flanged studs 25 carried by the disc 9. The rollers 24 are flangedas at Ma, see Figures 1 and 2, and the flanges 2M engage the ring 23rearwardly thereof for retaining the same rotatably on the disc 9.

The control device B, above described, is substantially entirelyenclosed in a streamlined shell 26 except that portions of the shafts i3and I4 protrude therethrough so that the blades l5 and I6 are disposedoutwardlythereof.

The hub ill of the control disc 9 is rotatably mounted on the outer endof a shaft 2'! which is concentric or axially alined with the axis ofthe propeller driving shaft 3, the shaft 21 being mounted in bearings28, 29 carried by the castings i forming part of the propeller head A.The forward end of the shaft 21 is provided with a screw thread 27a andthe bore of the hub I8 is correspondingly threaded for screw cooperationtherewith. Rotation of the control disc 9 relative to the shaft 21 willcause movement of the entire control device B axially of the shaft 27forwardly or rearwardly thereof, depending upon the direction ofrotation of the disc 9 relative to the shaft 21, for the length of thethread Zia.

Loosely mounted on the shaft 21 for rotation relative thereto is a wormsleeve 3%, the Worm thread of which meshes with the gears 3i and 3 l Asseen best in Figures 1 and 3, the gear 3| is keyed to a countershaft 32having keyed thereto a pinion 33 meshing with pinion 3d fixed to theinner end or base of the propeller blade 5. Similarly, the gear 3| iskeyed to a countershaft 32' having a pinion 33 keyed thereto and meshingwith a pinion 34' fixed to the inner end or base of the propeller bladei. The gearing just described running from the worm 35} to the propellerblades s and 5 comprise parts of the instrumentalities for causingrotation of the propeller blades 4 and 5 about their axes to change thepitch thereof and operate to rotate the propeller blades 4 and 5 inopposite directions of rotation about their respective axes and tomaintain these blades i and 5 always in the same phase of pitch.

The worm sleeve 36 is formed at its rear end with a hollow cone portion39a within which is received the cone element 35 fixed to the shaft El.The worm sleeve 30 is resiliently pressed axially rearwardly of theshaft 2? so that the cone element 35 is frictionally engaged with thecone portion file by means of the spring 35 interposed between the wormsleeve 3E and the freely rotatable race Sla of a thrust bearing 5?, theouter race Ell) of which is directly carried on the shaft 2i in fixedposition thereon. It will be apparent that with this construction oneend of a the spring 36 bearing against the worm sleeve 36, the other endof the springbearing against the freely rotatable race 37a of thebearing 31, the spring 1% and worm sleeve 3i! may rotate relatively tothe shaft 2'! while at the same time the cone portion 36a is pressedinto frictional engagement with the cone element 35 whereby a yieldableconnection between the worm sleeve 36 and the shaft 2's is effected forenabling rotation of the shaft 2i to cause rotation of the worm sleeve36 under normal conditions.

As seen best in Figure l, centrifugal brake instruinentalities areprovided for directly connecting the propeller head i with the controldisc 9 for rotation of the latter in positive connection with thepropeller head K under certain conditions. These centrifugal brakeinstrumentalities comprise centrifugal brake elements or weights 38 andiii? in the form of pistons slidahle in cylinders 3i? and 39, the axesof which are disposed radially of the shaft 2? so that the centrifugalpiston brake elements 38 and 36 are reciprocally movable in saidcylinders radially of the axis of the shaft 2?. The cylinders 39 and 39are carried by arms id and :0 secured to the gear casting l of thepropeller head A. The centrifugal brake elements 38 and 38 are providedwith rollers ll and ll engageable with the periphery of a disc 42secured to the hub ill of the control disc 9.

- Said hub it also carries a freely rotatable disc 43 tive to the hubIE. The centrifugal brake elements 38 and 38 are pressed radiallyinwardly toward the axis of the shaft .21 by means of springs disposedin the cylinders 3-9 and 39' and acting upon the centrifugal brakeelements 38 and 38 in opposition to the action of centrifugal forcethereof during rotation of the propeller head A.

In Figure l the disposition of the control disc 9 axially of the shaft2'? is such that the disc 42 is positioned for engagement with theroller members ii and ii of the centrifugal brake elements 38 and 33. Itwill be understood, however, that rotation of the control disc '9relative to the shaft 27 to move the control disc 9 axially rearwardlyof the shaft will bring the freely rotatable disc 43 into position forengagement thereof with the rollers ll and ti. Engagement of the rollersM and 4 l with the disc d3 will not, of course, afford and positiveconnection between the propeller head A the control device B, so thatunder such condition the propeller head A and the control device B mayeach rotate relatively to one another.

For a full understanding of the interaction of the centrifugal elementsE? and the springs l8, eference is now made to Figures 2, 4, 5, and 6particularly. In Figure i the spring [8 is diagrammatically representedas if its opposite ends were in engagement respectively with the blockor backing plate i2 and the centrifugal elements II, but with noexternal pressure applied to the spring is, and under this condition thespring is not applying any force to the elements l2 and ii. Thediagrammatic showing of Figure 4 represents centrifugal element H as ifits center of grav ity a:" were positioned at the center of rotation,indicated the lin 59, of the control disc 9. The shoulder or seat l'icprovided at the inner end of the counterbore ilb for seating the end ofthe spring it engaging the centrifugal member i! is disposed so that theend of the Spring engages the centrifugal element I? at its center ofgravity and in Figure 4 this is represented at the center of rotation 58of the disc 9. In Figure 5 the centrifugal element I! and the spring isare shown in their normal disposition as when the disc 9 is at rest, thecentrifugal element l1 being positioned at the inner end of the radialslot 9 i at its extreme limit of movement radially inwardly toward thecenter of rotation. Under such condition the center of gravity cc of thecentrifugal element ii is disposed radially outwardly from the center ofrotation 50 by th distance a and correspondingly the spring l3 has beencompressed the same distance. In Figure 6 the centrifugal element 5? andthe spring i8 are shown as when the element H has been moved outwardlyradially a distance 2a from the center of rotation 59. The spring iscompressed the same distance, and is thus pressed with twice the forcewith which it was pressed under the condition illustrated by Figure 5,since the produced force of the spring 28 is proportional to distance bywhich it is stressed (in this case compressed). In the operation of thedevice, of course, the weight it moves outwardly to the positionillustrated by Figure 6 under the action of centrifugal force only whenthe disc 9 is rotating above constant speed. In the rotation of the disc9 the centrifugal force produced by the element I! at the position shownin Figure 6 is twice the centrifugal, force produced by the element whenin the position of Figure 5 since the centrifugal force of the elementI! is proportional to its radius of rotation.

The arrangement of the spring [8 is such that its axis extends radiallyof the center or axis of rotation of the disc 9 and the spring I8 isdisposed so that its radially inner end would lie at the center or axisof rotation with the spring 18 in unstressed condition. Thus the spring:8 is ar ranged so that it is stressed by a force initially appliedthereto at the center or axis of rotation and acting upon the spring itfrom the center or axis of rotation radially outwardly therefrom.

The centrifugal element H is arranged for movement radially of the disc9 along the axis of the spring l3, and the element l! is disposed sothat it engages the radially inner end of spring l8 at the center ofgravity of the element ll.

Thus the relation of the parts i? and I8 is such that the radius ofrotation of centrifugal element IT is the distance by which the springI8 is compressed along its axis of length. This relationship alwaysexists irrespective of the radial position of the element H.

In View of the initial compressed condition of spring I8 it has a forceopposing radial outward movement of the centrifugal element H. Thespring force will exceed the centrifugal force of the element ll untildisc 9 attains a certain rotational speed, at which rotational speed thecentrifugal force of the element i! will equal force of the spring 18,and at rotational speeds above said certain rotational speed, thecentrifugal force of the element I! will exceed the force of the springl8.

Operation of control device The centrifugal element I! and the spring [3are calibrated so that the produced force of the spring it (due tocompression thereof) opposing radial movement of the centrifugal elementll outwardly of the disc 9 equals the centrifugal force of the element Hat a predetermined speed of rotation of the disc 9, which predeterminedspeed of rotation is the constant speed at which it is desired to causethe propeller shaft 3 to retate for uniform operation.

In view of the foregoing calibration of the centrifugal element i7 andthe spring iii, the produced force of the spring it exceeds thecentrifugal force of the element ll at any speed of rotation of the disc9 below the said predetermined constant speed of rotation. Consequently,the centrifugal element I! will not move outwardly radially of the disc9 from the position shown in Figures 2 and 5 until the speed of rotationof the disc 9 exceeds the predetermined constant speed, while thecontrol vanes i5 and K6 are at their minimum pitch of 20 e. g., seeFigure 7.

The control vanes l5 and [6 are designed to cause rotation of thecontrol disc 9 at constant speed at a predetermined speed of the airstream acting upon the vanes 55 and Hi to cause rotation of the disc 9when the vanes l5 and it are at their minimum pitch of 26. For example,in th use of the construction illustrated in Figure 1, the control discii may be designed to attain a constant rotational speed of, forexample, 32 R. P. S. when the plane upon which the control is mounted istraveling at an air speed of 32 miles per hour, see Figure 11. The saidconstant speed of rotation of the disc 9 will be attained at thepredetermined air speed when the vanes I5 and is are at their minimumpitch of 20.

Now it will be understood from the foregoing that since the control disc9 may attain its constant rotational speed of 32 R. P. S. at an airspeed of 32 miles per hour with the vanes l and I6 at minimum pitch of20, there will be no outward movement of the centrifugal element 11radially of the disc 9 until the air speed of the airplane exceeds thepredetermined air speed of 32 miles per hour, tending to cause the disc9 to rotate faster than the predetermined constant speed of 32 R. P. S.while the vanes i5 and i9 remain at their minimum pitch of 20.Nowbearing in mind that the produced force of the spring l3 exceeds thecentrifugal force of the element ll when the rotational speed of thedisc 9 is below constant speed and that the'spring force equals thecentrifugal force of the element I! at the predetermined constant speedof rotation of the disc 9 and that the centrifugal force of the elementI! exceeds the spring force of the spring is when the disc 9 rotatesfaster than the predetermined constant speed, it will be understood thatthere will be no radial outward movementof the element I! from theposition shown in Figures 2 and 5 until the air speed exceeds 32 milesper hour, tending to rotate the control disc 9 faster than thepredetermined constant speed of 32 R. P. S. while the control vanes I9and 19 are at minimum pitch of 20.

Thus the operation of the control device is such that it attains itspredetermined constant speed (for example 32 R. P. S.) at apredetermined minimum air speed (for example 32 miles per hour) actingupon the control vanes to cause rotation of the control disc 9 while thecontrol When the predetermined minimum air speed (for example 32 milesper hour) is exceeded, this tends to cause rotation of the disc 9 toexceed its predetermined constant rotational speed. The centrifugalforce of the element I? at this point exceeds the opposing force of thespring 19 so that the element l1 tends to move radially outwardly of thedisc 9. Radial outward movement of the element ll increases the pitch ofthe vanes I5 and 16 due to the action of pin 29 in helical slot l9causing counterclockwise rotation I of the vanes, referring to Figure 7,about the axes of their shafts I3 and I4. Increasing the pitch of thevanes 15 and It decreases the angle of attack of the air stream uponthem, thus decreasing the torque force, causing rotation of the disc 9and that results in decreasing the rotation of the disc 9 towardconstant speed.

As the rotation of the disc 9 decreases to constant speed, the element['7 will move radially inwardly of the disc 9 slightly, decreasing thepitch of the vanes i5 and i9 and increasingthe angle of attack of theair stream upon the vanes, which, in turn, increases the torque forcetending to rotate the disc 9, which acts to stop the decrease ofrotation of the disc 9 when the constant rotational speed thereof isagain attained. It will be understood, of course, that radial inwardmovement of the element l! causes clockwise rotation of the vanes,referring to Figure 7, about the axes of their vane shafts l3 and I4.

When the disc 9 is brought back to its predetermined constant rotationalspeed from a higher speed in the manner just described, the disc 9 willthenceforth continue to rotate at the constant speed so long as theparticular air speed (above the predetermined minimum air speed) ismaintained. It will be understood also that under this condition of airspeed higher than the predetermined minimum air speed, the disc 9 100- ivanes are at minimum pitch (for example 20). 1

10 tating at constant speed, the particular radial position of theelement IT appropriate to the new assumed pitch angle of the vanes i5and IE will be maintained until the further change in air speed occurstending to cause variation in I the rotational speed of the disc 9 fromthe predetermined constant speed.

Thus it will be seen that for every given air speed to which the controldevice is subjected above the predetermined minimum air speed, thecontrol vanes l5 and i6 will assume a certain position of higher pitchnecessary to produce the torque force required to rotate the disc 9 atthe constant speed for the given air speed, and the element ll will havea" corresponding radial position which will be maintained as long as thedisc rotates at constant speed and the air speed continues at thatparticular higher speed.

Irrespective of the radial position'of the element ll relative to thedisc 9, the centrifugal force of the element H will equal the opposingforce of the spring l9 so long as the disc 9 rotates at thepredetermined constant speed. For explanation, reference is again madeto Figures 5 and 6. In Figure 5 the centrifugal force of the element ITand the opposing force of the spring i8 were equal when the disc rotatedat constant speed, the element it remaining at its extreme inward radialposition in respect to the disc 9. In Figure 6, with the disc 9 stillrotating at its predetermined constant rotational speed, the centrifugalforce of the element ii is twice as large as the centrifugal force ithad in the condition of Figure'5 (since in Figure 6 the element i? hasthe radius of rotation 2a twice as large as its radius of rotation a ofFigure 5); likewise, in Figure 6, the opposing force of the spring istwice as large as the force it had in Figure 5 (since in Figure 6 thespring 59 is compressed a distance 2a, twice the distance a of Figure5). Thus, it will be seen that when the disc 9 is rotating at'itspredetermined constant speed, the equality between the centrifugal forceof the weight I! and the opposing force of the spring i9 is notafiec'ted by the radial position of the element ii; and also air speedsabove the predetermined minimum at which the disc attains itspredetermined constant speed do not affect the rotational speed of thedisc. At air speeds above the said predetermined minimum airspeed (forexample, 32 miles per hour), the pitch of the control vanes i5 and I6ischanged' in accordance with the torque force required to maintainrotationoz" the disc 9 at the predetermined constant speed, for example,32 R. P. S. It is only when rotation of the disc 9 varies from itspredetermined constant rotational speed that the centrifugal force oftheelement ii and the opposing force of the spring it become unbalanced.

Now assuming that the air speed to which the control device is subjectedis above the predetermined minimum air speed (for example, assume thatthe air speed is miles per hour and the disc 9 is rotating at constantspeed), the pitch of the vanes i9 and it has been automatically adjustedin the manner previously described by the radial positioning of theelement ii, to produce the torque force required to maintain the disc 9rotating at its predetermined constant speed. The air speed is nowdecreased to 69 miles per hour. Under this condition the pitch of thevanes l5 and I9 is not too high to maintain the constant rotationalspeed of the disc at this decreased air speed. The rotation of theaeeaoae disc- 54 tends to decrease to a rotational speed below thepredetermined constant rotational speed. The force of the spring 58nowexceeds the centrifugal force of the element I! causing the latter tomove radially inwardly relative to the disc 9, thereby decreasing thepitch of the vanes 55 and is, thereby increasing the angle of attack ofthe air stream acting upon the vanes and increasing the torque forcecausing rotation of the disc 9, and that results in increasing therotation of the disc 9 toward constant speed.

As the rotation of the disc 9 increases to constant speed, the elementIT will move radially outwardly slightly, slightly increasing the vanepitch, decreasing the angle of attack of the air stream and decreasingthe torque force to stop the increase of disc rotation when the constantrotational speed isagain attained.

General operation In the operation of an airplane, it is desirable tokeep the pitch of the propeller blades at low pitch until the propellerattains a predetermined speed of rotation and until the airplane attainsa. predetermined minimum forward speed. The reason for this is that atlow rotational speed of the propeller and at low: forward: speed or theairplane, high pitch of the propeller blades produces low efficiency ofthe propeller. In accordance with the invention, therefore, brakeinstrumentalities, previously described, are provided for positivelyinterconnecting the control disc 9 for rotation with the propeller driveshaft 3. so

that there will be nov relative rotation between the control disc 5% andthe propeller shaft 3 u-ntil these instrumentalities attain apredetermined rotational speed.

If it were not for the provision or the brake instrumentalit-ies, andthe propeller shaft 3 were allowed to. rotate relatively to, the controldisc 9 at the commencement. of propeller rotation, the result wouldbethat with the airplane standing still on the ground, and the throttleopen, there would be little or no torque force tending to rotate thecontrol disc t? and the propeller shaft 3 would rotate relativelyfaster, which relative rotation would be effective to in;- crease thepitch of the propeller blades to their maximum. The provision. of the.brake instrumentalities above mentioned prevents this situation fromoccurring and enables the propel- Ier shaft to attain a. predeterminedrotational speed before the control device, becomes effective toincrease the pitch of the, propeller blades.

While it is desirable to keep; the propeller blades at low pitch untilthe propeller shaft 3 attains a relatively high speed approaching thepredetermined constant speed, it. is not practicable to provide for thebrake instrumentalities to be efiective to maintain. the propellerblades at low pitch for all rotational speeds. ofthe propeller shaft upto the predeterminedconstant speed', because if the brakeinstrumental-ides were only to become ineffective. at or above thepredetermined constant rotational speed, then the brakeinstrumentalities would become effective whenever the rotational speedof the propeller shaft drops below. the predetermined constant speedeven through: at. such time the pitch of the propeller blades. happensto be at high or maximum pitch. This would prevent the control devicefrom operating to decrease the pitch of the propeller blades when therotational speed of the propeller shaft droppedbelow constant speed eventhough at such time the pitch provide that the brake instrumentalitiesbecome effective to couple the control disc 9 with the propeller shaft 3at a rotational speed of the latter some-what below predeterminedconstant rotational speed in order to provide a range of rotationalspeed below the predetermined constant rotational speed within whichrange the control device may operate to change the pitch of thepropeller-blades. it is for this reason that the brake instrumentalitiesare preferabl designed so that the centrifugal brake members 38 and 38'will move outwardly so as to release the propeller shaft 3 from anyinterconnection with the control disc 5i whenever the propelle shaft 3attains a rotational speed of approximately 90% of the predeterminedconstant rotational speed.

Now describing the general operation of the structure as when in actualuse upon airplane, we will assume that the control device B is designedto attain a rotational constant speed of 32 R. P. S. an air speed of 32miles per hour; that is when the airplane has a forward speed of 32miles per hour. We will assume, also, that the airplane is standingstill and the engine is at rest. The propeller blades 1i and t are atlow pitch and the control disc 9' is disposed axial ly of the shaft 2?so that the rollers ll and 4'!" are in engagement with the freelyrotatable disc 43 on the hub It of the control device. As soon as theengine is started, the propeller shaft 3 will rotate counter-clockwise,looking toward the left of Figure l, the propeller hub i will rotatecounterclockwise, referring to Figure 3, and the shaft 2? will likewiserotate counterclockwise, referring to Figures 52- 3. Since the disc 9 isat rest, the shaft 2? will be caused to rotate relative to the hub, it.on account of the threaded connection between the shaft 2i and hub in,the control device 13' will he caused to move axially rightwardlyrelative to the shaft 2i, referring to Figure 1, so that the rollers itand :3! will be engaged with the disc 52 in the condition shown inFigure 1, since the axial movement of the control device B. relative toshaft 2? continues until the disc 9 abuts the washer 2Tb at the forwardend of the 21.

Now the control device 33 is locked to the pro peller drive shaft 3through the brake in.- strumentalities including rollers M and llengaging the periphery of the disc d2 that the disc 3! rotates with thepropeller shaft This locked condition continues to exist until thepropeller drive shaft 3 attains the rotational spec of 90% of thepredetermined: constant rotati speed, at which time centrifugal force ofthe weights 38 and 33 overbalances the opposing force of the springs :35permitting the weights 38 and 38 to move radially outwardly, causing therollers all and M to become disengaged from the disc i2, permitting thepropeller drive shaft 3 and the propeller head A new to rotateindependently of the control device B. If at this time the propellerdrive shaft 3 and the propeller head A tend to rotate faster than thecontrol disc 9, the result will be that the pitch of the propellerblades Q and 5 will be increased, causing decrease in rotational speedof the propeller shaft 3 rotates, faster than the control disc movementof the propeller blades through the air at the increased pitch. As.long. as the propeller shaft 3 rotates faster that the control disc 3the pitch of the propeller blades and is will continue to be increased,to a, higher pitch. This will cause slowing down of the rotational speedof the propeller shaft 3 until the rotational speed falls below 90% ofthe predetermined constant rotational speed at which time the brakeeletil the rollers 4i and 4! again engage the disc 42, whereupon thepropeller shaft 3 will again be locked to the control disc 9 forrotation of the disc 9 with the propeller shaft 3.

Aslong as the airplane is standing still on the ground, there is littleor no action of the air upon the control vanes l and It to tend torotate the control device B so that whenever the propeller shaft 3exceeds 90% of the constant rotational speed, the brakeinstrumentalities are freed from the disc 42, allowing the propellershaft 3 to rotate independently of the control disc 9. As soon as thisoccurs, the rotational speed of the disc 9 will immediately decreasebecause there is no torque force tending to maintain its rotation. Asthe rotational speed of the disc 9 decreases relative to the rotationalspeed of the propeller shaft 3, the effect is to rotate the shaft 21relatively to the propeller shaft 3. This in turn will cause rotation01" the worm sleeve 3e frictionally connected to the shaft 2?, and theworm sleeve 38, being in mesh with the gears 3| and 3|, will set thegear trains 3|, 33, 34, and 3!, 33 and 34 in operation to rotate thepropeller blades 4 and 5 about their axes to increase the pitch thereof.

Thus, since the control disc 9 is locked to the propeller shaft 3 untilthe latter attains a rotational speed of approximately 90% of thepredetermined constant rotational speed, the control device B isineiiective to increase the pitch of the propeller blades 4 and 5 fromthe slow pitch thereof existing at the time of starting the engine untilthe rotational speed of the propeller shaft 3 attains or exceeds 90% ofthe predetermined constant rotational speed. Also, whenever thepropeller shaft 3 rotates faster than 90% of the predetermined constantrotational speed,

and the brake instrumentalities are freed from the disc 42, there willbe insufiicient torque force acting upon the control vanes l5 and i 6 tomaintain the rotational speed of the disc 9 at or above 90 of thepredetermined constant rotational speed until the airplane attains acertain forward speed. The explanation for this is seen by reference toFigures 9 and 10. With the control vanes i5 and iii at minimum pitch of20% at low air speeds such as illustrated in Figure 9, the angle ofattack of the air with reference to the control vanes is such as to hitthe vanes on their back sides, producing a positive pressure rearwardlyof the vanes and a negative pressure forwardly thereof, resulting in alift force L acting in the direction of the arrow in Figure 9 andproducing a torque force tending to stop rotation of the disc 9. On theother hand, at the higher forward speed B of the airplane, asrepresented in Figure 10, the air stream acts to hit the control vane onthe forward side, producing a lift L in the direction of the arrow inFigure 10 and a resultant torque force acting to produce rotation of thecontrol disc 9.

As represented graphicaly in Figure 11, the design of the control vanesi5 and i6 may be such -that when the pitch thereof is 20, the airplanewould have to attain a forward speed of, for example, about 26 miles perhour before the air stream would have an angle of attack such as to hitthe blades from the front to produce a torque force to cause rotation ofthe control disc 9. In

accordance with this example, when the forward ments 38 and 38 will moveradially inwardly unspeed of the airplane exceeds the minimum speedrequired to produce independent rotation of the control disc 9 at about26 miles per hour, the propeller shaft 3 will be allowed to increase itsrotation gradually above of constant speed until the control disc 9attains its predetermined constant rotational speed of, for example, 32R. P. S. at a forward speed of the airplane of about 32 miles per hour.

During the period that the airplane is ncreasing in speed from theminimum air speed which will produce independent rotation of the controldisc until the control disc d attains its predetermined constant speed,the control device 13 will act to vary the pitch of the propeller bladest and 5 as necessary to cause the propeller shaft 3 to rotate at thesame speed of rotation as the disc 9.

Now as above mentioned, the control vanes i5 and it are designed so thatthe control disc 9 will attain its predetermined constant rotationalspeed at a predetermined minimum air speed while the control vanes i5and it are at their minimum pitch of 20. In other words, for reasonsabove mentioned, it requires a predetermined minimum speed of the streamacting in front of the control vanes it": and it in order to produce thetorque force necessary to rotate the disc 9 at the predeterminedconstant rotationalspeed. This predetermined minimum air speed orminimum forward speed of the airplane at which a disc 9 will be causedto rotate at the predetermined constant rotational speed may, forexample, be an air speed of 32 miles per hour as graphically illustratedin Figure 11. Once the airplane attains the predetermined minimum airspeed of 32 miles per hour, the disc 9 will rotate at the predeterminedconstant rotational speed of 32 R. P. S. as long as the airplane has aforward speed of 32 miles per hour, or above. Since, under thiscondition, the brake instrumentalities are disengaged and the controldisc 9 and propeller shaft 3 are permitted to rotate independently ofone another, whenever the rotational speed of the propeller shaft 3tends to vary from the predetermined constant rotational speed of 32 R.P. S., the control device B will be effective to change the pitch of thepropeller blades 3 and 5 to bring the rotational speed of the propellershaft 3 back to the predetermined constant rota-- tional speed. If, forexample, the rotational speed of the propeller shaft 3 tends to exceedthe predetermined constant rotational speed of 32 R. P. the control disc9 will impart a relative clockwise rotation to the shaft 22-, referringto Figures 2 and 3, so that, in effect, the shaft 2 is caused to rotateclockwise relatively to the propeller shaft 3, assuming tie the controldisc 9 and propeller shaft 3 are both rotating counterclockwise,referring to Figures 2 and This relative clockwise movement of the shaft2'! with respect to the propeller shaft 3 will result in increasing thepitch of the propeller blades 3 and 5 so that they will absorb moreenergy under greater resistance or load, causing the speed of rotationof the propeller shaft 3 to decrease to the constant speed set by thecontrol device B.

On the other hand, if the rotational speed of the propeller shaft 3tends to decrease from the constant speed set by the control device B,the disc 5 will, under such conditions, efiectively cause rotation ofthe shaft 2'7 in a coimtercloclcwise direction relative to the rotationof the propeller shaft 3. Assuming that the parts were in thedisposition of Figure 1, except that brakes ii-4i were free from disc42, of course, the preliminary result of relative counterclockwiserotation of the disc $3 with respect to the propeller shaft 3 would beto cause axial movement of the disc s and its hub leftwardiy relative tothe shaft 2'5, referring to Figure 1, due to the threaded connectionbetween shaft 2? and hub at, until the shoulder itb of the hub i6 iscaused to abut with the shoulder of the shaft 2?, whereupon the relativecounterclockwise rotation of the disc 9 is then imparted to the shaft Eland this acts through the worm sleeve 36 and gearing associaetdtherewith to effect decrease of the pitch of the propellcr blades s andso that they absorb less energy under less resistance or load to th rebypermit the propeller shaft 3 to increase its speed of rotation until itresume." the predetermined constant rotational speed set by the controldevice B.

It is desired to describe the operation when the airplane rought in fora landing after a flight. When the plane is to be brought in for a thepilot closes the throttle which slows down the engine w th suddendecrease in rotational speed of the propeller shaft 3, while the controldisc ti continues to rotate at constant rotational speed until the airspeed decreases below the predetermined minimum air speed. W hen ththrottle is closed for landing, it is desirable, of course, that thepropeller blades s and 5 concurrently adjusted to minimum pitch. Thereason for this is that the landing may have to be broken off on accountof some unforeseen. dangerous condition when the plane is close to theground and the propeller, therefore, should be adjusted so that, ifnecessary, the engine can attain high speed very rapidly when thelanding has to be broken off. and the throttle is opened when the planeis close to the ground. The engine can attain high speeds more rapidly,of course, if the pitch of the propeller blades is at minimum pitch.

Now is will be recalled that the brake instrumentalities above describedgo into operation when the propeller shaft 3 rotates at or below 88% ofthe predetermined. constant rotational speed; that is to say, that thecentrifugal brake elements as more radially inwardly until they are attheir inward limit of radial movement when the propeller shaft a isrotating at or below 90% of its predetermined constant rotational speed.Now when the pilot closes the throttle for landing, if the brakeinstrumentalities were to become effective for locking the control disc5; to the propeller shaft 3 when the latter slows down to 90% of itspredetermined constant rotational speed, there would be not enough timefor the control disc 8 to decrease the propeller pitch to minimum beforethe control disc s became locked to the propeller shaft For this reasonthe freely rotatable disc 53 been provided, and provision is made foraxial shifting of the disc s and its hub is rearwardly under suchcondition, so that when the propeller shaft 3 has been operating atabove 90 of its predetermined rotational speed, and is slowed down to 90of its constant rotational speed, the radial inward movement of thecentrifugal element 35 causes the rollers ll and ll to engage the disc:13 rather than the disc :12, and such engagement enables the controldisc 8 to continue to rotate independently of the propeller shaft 3 sothat the control disc 9 will be effective to decrease t1 e pitch of thepropeller blades t and, 5 to their minimum as the propeller shaft 3slows down. For explanation, let us assume that a propeller shaft. 3 andcontrol disc 9 are rotating at mined constant rotational predeterminedconstant rotational speed, with the airplane driving forwardly atcruising speed with the propeller blades 3 and at relatively high pitch.Now under such conditions when the pilot closes the throttle forlanding, the rotational speed or the propeller shaft 3 decreasesrapidly, while, due to the forward speed of the airplane, the controldisc E3 continues to rotate at higher rotational speed than thepropeller shaft 3. On account of the threaded connection between the hubit and the shaft 2?, this faster rotational speed of the control disc swill cause the same to move axially of the shaft 2? leftwardly, refering to Figure 1, until the shoulder lilb abuts the shoulder 2'50 on theshaft 27, at which ti e the freely rotatable disc 23 will be positionedfor engagement with the rollers s! and. it, when the rotational speed ofthe propeller shaft 3 drops down below l0% of its predeter- As beforementioned, when the control disc 9 rotates faster than the propellershaft 3, after the axial movement of the hub ltl relative to shaftcauses abutment of shoulder it"s with shoulder tie, the control disc 9will be effective to rotate the shaft 2? to cause decrease of the pitchof the propeller blades 4 and 5. Under the conditions now beingdiscussed, where the rotational speed of the propeller shaft 3 dropsfrom a higher speed down to a rotational below of its predeterminedconstant rotaticnal speed, the faster rotation of the control disc 3will be efiective to cause decrease of the pitch of the propeller bladesl and l"; to their minimum. On the other hand, whenever the rotationalspeed of the propeller shaft 3 increases from the lower speed up to orabove 90% of its prcdeterminec constant rotational speed, the disc l2will be positioned for engagement with the rollers il and so long as therotational speed of the propeller shaft 3 is increasing or tends torotate faster than the control disc s.

It will be noted that gears ti and 55! are provided with abutmentmembers 55 which are arranged for abutting engagement with abutmentmembers 55 secured to the housing i for limiting the pitch changingrotation of the blades and 5 about their axes. Since a hard run into thelimiting abutting engagement might damage the gearing, a cushioning slipconnection between the worm sleeve as and the s. aft 2? is provided.When the disc 9 rotating at high speed faster than the propeller shaft 3is in action to relatively rotate the shaft ii to decrease the pitch ofthe propeller blades s 5, the worm sleeve 2 will produce a constantpressure against the spring 33. The spring pressure normally greaterthan the opposing pressure of the worm sleeve. However, when the members55 and 56 come into abutting relation, the rotation of the gears 32 and3! is stopped and the force is transmitted to the worm sleeve 38, thisforce, now being greater than the spring force, causes the spring 35 toyield, loosening the frictional engagment of the sleeve port it le withthe cone 35, permitting the shaft 2? to rotate relatively to the wormsleeve st to the extent necessary to equalize the force acting on theworm sleeve with that of the spring In other words, the worm sleeve aswill only loosen so much that the sl pping resistance of the cone 35 inthe sleeve gives enough torque force on the. sleeve as so that thescrewing force of the worm 3b is equal to the pressure of the spring 36.The slipping of the cone 35 in the sleeve 17 30 acts as a brake force onthe conel35 which will'result in slowing down the rotation of thecontrol disc 9 to the rotational speed of the shaft 3 under theconditions now being referred to.

Damping means Figures 14 to 16 inclusive illustrate a modification ofthe form of the invention shown in Figures 1 to 3 inclusive, inreference to the provision of means for housing each of the centrifugalelements I! of the control device B in a respective housing adapted tobe filled with suitable substantially incompressible fluid, such aslubricating oil, serving to damp the radial movement of the elements I!and to provide lubricacation therefor.

As shown in Figures 14, 15 and 16, each of the centrifugal elements I1and its respective spring I8 is housed in a respective pair of cylinderhalves I and IOI which are secured to the disc 9 by means of bolts I02,each cylinder half, I00 and IN having a flanged portion I03 abutting thedisc 0 and provided with apertures, receiving the bolts I02. Thecylinder halves I00, I01 are machined to have a substantially oil-tightfit with the respective element II. The cylinder halves I00, IOI alsohave an oil-tight fit with the disc 9 and for this purpose suitablegasket means may be interposed betweenvthe flanged portions I03 and thedisc '9. Elements I! are provided with slots Ila (Figure 1) receivingportions of the disc 9 for guiding the radial movement of elements II,as above described.

Thus each pair of cylinder halves I00, IOI provides a cylindricalhousing for the respective centrifugal element I1 and its respectivespring I8, which housing is adapted to be filled with suitable hydraulicfluid, such as lubricating oil.

7 Each element II has machined into its periphery a longitudinal grooveIId extending longitudinally of the element II in the direction of theaxis of movementof the element I'I axially of its respective blade shaftI3. Groove IIdi provides a passage through which the fluid in thecylindrical housing I00, IOI can pass from one side of the element II tothe other side of the same whenever the element II moves radiallyof thedisc 9 in theoperation of the control device B. Each element I1 is alsoformed with a central sleeve portion IIe which closelyysurrounds theshaft part I3a with an oil-tight-fit that prevents the oil from flowingthrough groove I9.

Preferably the construction of the invention as disclosed in Figures 1through 3 will embody the modification of Figures 14 through 16, inorder to eliminate any tendency of the elements I! to over-correct thepitch of the vanes I5 and I6 which might otherwise exist but for thedamping effect of the fluid in cylindrical housings I00, IOI upon theradialmovement of the elements II.

In the operation of the control means of Figures 1 through 3 embodyingthe modification of Figures 14 through 16, the hydraulic fluid in thecylinders I00, IOI will slow down the radial movement of the centrifugalelements I! so that the pitch of the blades I5, I6 will be changedgradually to allow for lag in acceleration or deceleration of thecontrol disc 9 following such radial movement of the centrifugalelements II. This damping effect upon the radial movement of thecentrifugal elements II will thus eliminate any possible over-correctionof the pitch of the blades I5, I6 and consequent "hunting movement ofthe elements II which might otherwise 18 result from too rapid radialmovement of elements II without allowance for lag in acceleration ordeceleration of control disc 9.

It will be apparent also that the use of lubricating oil as thehydraulic fluid in each cylinder I00, IOI serves to lubricate themechanism housed therein in an oil bath.

The capacity of the groove I Id and the viscosity of the hydraulic fluidin the cylindrical housings I00, IOI will be calibrated so as toregulate the radial movement of the centrifugal elements II relative tothe rotatable member 9 in such a manner as to coordinate the speed ofradial movement of the centrifugal elements I! with the rate ofacceleration and deceleration of the rotatable member 9.

Modification construction In Figures 12 and 13 there is shown amodification wherein the constant speed control instrumentalities areincorporated in the propeller itself, and this construction is designedfor use on small airplanes where the necessary force for changing thepitch of the propeller blades is not too great.

In this construction the propeller drive shaft is indicated by thenumeral 60 and it has suitably secured thereto the propeller hub 6Iwhich is provided with radially and oppositely extending sleeve portions62 and 63 which receive the inner ends of the propeller blades 64 and 65mounted for rotation in said sleeve portions about the axes of saidblades for varying the pitch thereof.

Within each of the hollow cylindrical inner end portions 64a and 65a ofthe propeller blades is mounted a respective centrifugal weight element66 arranged for radial sliding movement in the respective hollowcylindrical portion of the blades. Each of the centrifugal elements 66is provided with outwardly extending guide pins 61 extending throughrespective longitudinal slots 68 in the cylindrical portions of thepropeller blades 64 and 65, and these guide pins 61 are provided attheir outer ends with guide rollers 69 arranged for cooperation withhelical grooves I0 provided in the respective sleeve portions 62 or 63.The inward radial movement of the centrifugal elements'66 with respectto the blades 64 and 65 is limited by abutment of the elements 66 withtheir respective plugs provided at the inner end of the cylindricalportion of each blade 64 and 65, the said plugs being designated by thenumeral II. Each of the elements 66 is provided with a central recess I2for receiving the spring I3. The recess I2 provides a seat I211 thecenter of gravity for engaging one end of the spring IS. The oppositeend of the spring I3 engages a bafile I4 provides in each of thepropeller blades 64 and 65, the baffle orrib I4 being provided with aseat-14a for receiving that end of the spring which is compressedbetween the baffle I4 and the centrifugal element 66 opposing radialoutward movement of the element 66 in the normal condition of the partsas illustrated in Figure 12 when thepropeller, is at rest.

While the spring I3 and centrifugal element 66 are only seen in respectto one propeller blade, namely blade 64, in Figure 12, it will beunderstood that these elements are duplicated in the other propellerblade 65.

The elements II provide on each of the blades 64 and 65 are formed asbevel gears having bevel gear teeth I5 meshing with a pinion 'I6 freelyrotatable on a stub shaft 11 carried by the proacet c-a2 i9 pellerrshaitto. This gearing ioetween'the blades Eli and 65 enables the same to berotated "about their axes Simultaneously for changing the :pitch thereofin the same phase relation.

The calibration of the spring '73 and centrifngal element 66 for eachpropeller :blade, and the arrangement of these elements with respect tothezcenter or 'axis of rotation of the propeller isith'e same as thatdescribed'in reference to the calibration and arrangement of thecorresponding elements in reference to the center or axis of rotation ofthecontrolsdisc :9. In otherwords, the axis of the spring 13 is"disposed radially of the center "of rotation *of :the propeller, whichis the axis of the'propeller shaft til, and the centrifugal element Stis disposed for :radial movement along the same radial line. Thearrangement of the spring '13 is such that its radially inner endengaged with the seat 1211 would lie at the center oraxis of rotation ofthe propeller with the spring l3 in unstressed condition. Thus, thespring, in the condition of Figure '12, is arranged so that'it isstressed by a force initially applied thereto at the center or axis ofrotation, which force acts upon the spring 13 from the center or axis ofrotation in a-direc'tion radially outwardly from the center or axis ofrotation.

'The centrifugal element 66 is arranged for movement radially of theshaft 69 along the axis'o'f the spring 13 and the element 56 isdisposedso that it engages the radially inner end of spring "I3 at thecenter of gravity of the element 65.

Thus the relation of the parts 65 and T3 is such that theradius ofrotation of thecentrifugal element 56 is the distance "by which thespring 13 is-compressed along its axis=or length. This relationshipalways exists irrespective of the radial position of the element 66.

"The centrifugal element '66 and its associated spring T3 are calibratedso that the produced force of the spring '13 -(due 'to compressionthereof) opposingradial movement of the centrifugal element "66outwardly of the propeller blad'e equals thecentrifugal force of theelement 66 at'a predetermined speed "of rotation of ithe propeller "andshaft 6%, which predetermined speedof rotation is the constant speed atwhich it is desired to cause the propeller 69 to 1'0- tate for uniformoperation.

Now describing the operation of the constructionof Figures 12 and-13,'it may be notedthat the centrifugal element 65 is normally disposedas shown in Figure '12 at its limit of inward radial movement, and underthis condition the blades'ii l and '65 'wiillbe at minimum pitch. Theelement will remain in this condition'until the propeller and shaftattain their predetermined constant speed of rotation, the spring 'forceof the 'spring'lt exceeding the centrifugal force of the'element filiuntil-the predetermined constant rotational "speed is attained, :atwhich time the forces become equal. If the propeller and shaft '50rotate faster than the predetermined constant rotational speed, thecentrifugal element 66 will tend to moveradially outwardly. Hence undersuch conditions the centrifugal force of the element "655 exceeds theopposing force of the springlS and radial outwardmovement of the element66 will cause the blades 64 and 65 to be rotated about their axes toincrease the pitch or the blades, due to the cooperation of the guiderollers :69 with-the helical slots 10. In other words, the'ra'dial move-20 merit of the centrifugal element 66 acts with :a screwing action torotate the same about its radial :axis and the guide pins li'i workingin the longitudinal .slot 1.68 will cause a corresponding rotation ofthe propeller blades E i and 55.

The increase in the pitch of the propeller blades t2 and occurring whenthe rotational speed of the propeller exceeds the predetermined constantspeed, serves to slow :down the rotation of the propeller to constantspeed. As the propeller rotates to slow down toconstant speed, thecentritugal element 66 will move radially inwardly slightly, decreasingthe pitch of the propeller blades 6'4 and. 6 5 to the point necessary.to maintain constant speed at the particular air speed of the airplane.Thus the centrifugal force of the element "65 and the force or" thespring i3 will be'again equalized when the propeller'rotation drops backto constant speed.

It will 'be noted that the centrifugal element 65 will have a radialposition for each particular air speed 'as long as the propeller andshaft til are rotating at constant'speed, which radial position =will bedependent upon the pitch of the propeller blades .6 3 and 65 "necessaryto maintain the rotation of the :propeller and shaft at predeterminedconstant rotational speed. As long as the propeller and shaft 6% arerotating at predetermined constant rotational speed, thecentrifugalforce of the element '66 and the force of the spring 13opposing radial outward movement thereof will be equal.

I am aware that there are prior propeller control constructions in whicha centfiifugal 'weight is arranged for radial outward movement bycentrifugal "force opposed by a spring and such radial movementc'f thecentrifugal weight is-used to vary the pitch of the propeller "blades.However, the special relationship between the spring and the centrifugalelement as herein disclosed is believed 'to' be novel.

It 'will be apparent that the modification of Figures 12 and 13 mayreadily avail of damping means, similar to'that-ofFigures 14 through :16applicable to the construction of Figures 1 through '3, whereby tocoordinate the speed of radial movement of the centrifugal elements ttwithrate of acceleration anddeceleration of the propeller 6I--"65-"so asto allow for lag in such acceleration or deceleration and eliminate anyhunting movement of the centrifugal element 66.

For this purpose it is only necessary "to fill the hollow portions =E4a,a, of the propeller *blades 54, with suitable hydraulic fluid suchaslubricating oil and to provide passages for the fluid from one side tothe other'of thecentrifugal elements 66, such as the passages providedby thegroovesild in reference to the elements H of theconstruc'tion of'Figures 1 through 3.

Having thus described my invention, what -I claim as "new and desire tosecure 'by Letters Patent "or the United "States, is:

lfMechanism of the class described, -comprising, in combination, arotatable member, 'a centrifugally responsive element carried therebyfor movement radially thereof, spring means yieldably-opp'osing radialoutward movement of said element and disposed with its axis extendingradially of the axis of rotation of said rotatable member, and meansresponsive to radial movement of said elementfor varying the torqueforce applied to'said rotatable member when its rotational speed variesfrom a predetermined rotational -speed, said element cooperating withsaid spring at'the center of gravity of said element with a force actingon said spring from said axis of rotation radially outwardly therefrom,

said element and said spring being arranged so that theradius ofrotation of said element is the distance by which the spring is stressedalong its axial length and means cooperative with said 'centrifugallyresponsive element for coordinating 'the speedof radial movement thereofwith the rate of acceleration and deceleration of the rotatable member.

' 2; Mechanism of the class described, compris- "ing, in combination, arotatable member, a centrifugally responsive element carried thereby formovement radially thereof, spring means yieldably'opposing radialoutward movement of said element and disposed with its axis extendingradially of the axis of rotation of said rotatable member, and meansresponsive to radial movement of said element for varying the torqueforce applied to said rotatable member when its rotational speed variesfrom a predetermined rotational speed, said element cooperating withsaid spring at the center of gravity of said element with a' forceacting on said spring from said axis of rotation radially outwardlytherefrom, said element and said spring'being arranged so that theradius of rotation of said element is the distance by which the springis stressed along its axial length, a housing for said cenjtrifugallyresponsive element, said housing constructed to permit said radialmovement of the centrifugally responsive element therewithin, a body ofsubstantially incompressible fluid filling said housing, means providinga passage through which said fluid may pass from one side of thecentrifugally responsive element to the other side thereof upon radialmovement of said centrifugally responsive element relative to saidrotatable member.

3; Mechanism of the class described, comprising, in combination, arotatable member, a centrifu'gally responsive element carried therebyfor movement radially thereof, spring means yieldably opposing radialoutward movement of said element and disposed with its axis extendingradially of the axis of rotation of said rotatable member, and meansresponsive to radial move-,

ment of said element for varying the torque force applied to'saidrotatable member when its rotational speed varies from a predeterminedrotational speed, said element cooperating with said spring at thecenter of gravity of said element with a force acting on said springfrom said axis of rotation radially outwardly therefrom,

said element and said spring being arranged so that'the' radius ofrotation of said element is the distance by which the spring is stressedalong its axial length, a respective housing for said centrifugallyresponsive element, said housing means providing a passage throughwhichsaid fluid may pass from one side of the centrifugally responsiveelement to the other side thereof upon radial movement of saidcentrifugally responsive element relative to said rotatable member, "thecapacity of said passage and the viscosity of said oil being calibratedto coordinate the speedof said radialmovement' of the centrifugallyresponsive element with the rate of acceleration and deceleration of therotatable member. 4. Mechanism of the class described, comprising, incombination, arotatable member, blade elements mounted thereon withtheir axes disposed radially thereof, centrifugally responsive elementscarried by the rotatable member for movement relative thereto radiallythereof, said centrifugally' responsive elements cooperating with theblade elements to rotate same about their axes to vary the pitch thereofupon radial movement of the centrifugally responsive elements, andresilient means associated with the centrifugally responsive elementsfor opposing outward movement of the latter radially of said member,said resilient means being stressed by axis of rotation of the rotatablemember radially outwardly from said latter axis, said resilient meansand said centrifugally responsive elements being arranged so that theradius of rotation of the latter is the distance by which the resilientmeans is stressed to produce the force opposing radial outward movementof said centrifugally responsive elements.

5; Mechanism of the class described, comprising, in combination,supporting means, a propeller therefor mounted for rotation thereon, acontrol device comprising a rotatable member mounted on said supportingmeans for rotation independently of said propeller, about an axis alinedwith the rotational axis of said propeller, vane elements mounted onsaid rotatable member with their axes disposed radially thereof,centrifugally responsive elements carried by the rotatable member formovement relative thereto radially thereof, said centrifugallyresponsive elements cooperating with the vane elements to rotate sameabout their axes to vary the pitch thereof upon radial movement of thecentrifugally responsive elements, and resilient means associated withthe centrifugally responsive elements for opposing outward movement ofthe latter radially of said member, said resilient means being stressedby cooperation with said centrifugally responsive elements at the centerof gravity thereof with a force acting upon the resilient means from theaxis of rotationrof' the rotatable member radially outwardly therefrom,said propeller having propeller blades mounted thereon for rotationabout their axes to vary the pitch thereof, and means interconnectingsaid rotatable member and said propeller blades for rotating the sameabout their axes responsive to a variation between the rotational speedofthe propeller and the rotational speed of said rotatable member.

6. Mechanism of the class described, comprising, in combination, arotatable member, a centrifugally responsive element carried thereby formovement radially thereof, spring means yieldably opposing radialoutward movement of said element, and disposed with its axis extendingradially oi the axis of rotation of said rotatable member, saidcentrifugal responsive element being associated with the rotatablemember for movement radially thereof along the radial axis of thespring, and means responsive to radial movement'of said element forvarying the torque forc applied to said rotatable memberwhen itsrotational speed varies from a predetermined rotational speed, saidelement cooperating with said spring at the center of gravity of saidelesnemberp-onoimenns v t ine soidimemoerot oi to iono spee which e-f noonof itssp e o f linear travel, including means responsive .to radio;movementgof said. element for varying the torque ,force applied :to saidrotatable member whenitsrotational speed va.ri es from apredeter-IlljllQd rotational speed, said-element coop erating lwithseid sprin =e..t e c t r of r vity of said element with a- K foroetacting onsaidsprlng from said exis of .rotetionpf the rotatable member,

l tad allyutwnr lyiroms l-idtlot r ox srsamen (a d ,saidleprlne in rr nd so tha radius of rotationof said element lsithedistance by whichthespring vis stressed along its axial leng h.

,8. MeohaniSmQf the .classdescribed, comprisins, i roomb netion, a rotable member, "a e trlf go lly ,responsive element carried thereby formovement radially thereof, resilient means yield only opposingradialoutward movement of said element, and means responsive to radialmoviemfintlof seidelementfor varying thetorquelforce a pl e to sairototarble member whe its ototione sneed v ries i qrn a predete m n d rta tio al speed, sold es l e means heme stressed (by ooooe it on vw hiiol l men .itt the .oen of gravity thereof with a fo e no n open hresilient mea from the is of rot tio v of the rotatable member radiallyoutwardly from said latte axis, sold resili nt me n E nds id elemen .oeis an ed so that t e d us of rot tion of the lett ls e distance by wh chth r sili nt mean t es d to produce the or e oppos ng redial ou ward movment of said lem nt.

,9, lyleohenism of the class described, c mpris- ,,in in .oombin tion popell r pporting m ans, l=

a p o ll r he ef r mounted for rotation thereon, a rotatabl w,roembn munted on said ppo t ng mean f r tation in e en ently ofs id hroplel or,a ieentrli olly responsiv elemen c r- .rie :by sold rotat ble membe ormovement initial y ther of, r silient moons ,yie dn y opposins l clletlout vzsrd movement .of said element means o ot te said rotatable membeat i tational speed which is a functionpf the speed o l-iosli y travelof sa d su ort n m ans, said on il ega y resp ns v re ement c operat n wth sol .mtotionm ens to vary the o que force anllliecl thereb t rotatethe r tatable member v. ipon radial mov ment of said cen rifu al el soldres ient "means be n st ess d :by c

4,0. ,Me honism'of the olossidesoribedwoomnrisins, in combination,propeller si nn rtin rmeam, a p op ller therefor m unted Lforarotationethereon end having v arlable pitch -,pron611 e r i'blaidfis, arotatable member mounted on said supporting me ns 101' rotationindeponclent y of said nrospeller, o loentrifugal y .responsive elementloo-r" lied by said rotatable member 1-for movement radi lly thereof,resilient ,means-yielda ly oppo ing radial outward movement of saidelement, variable pitch blade elements oarried-byzsaidiro tatable memb r:for ,-;rota ins the some 1 1 18 z ,infiuenoe of the pressure oatmospheric: oi-r notthereon incident to bodily vEmov,eme l'nof 1th?supporting means, means responsive 7 media movement or :Saidioentrifugally r sponsive rfile mentforivarying thepitch-vqfl-sald-blade elements, said resilient means being :stressed zbycooperation with said oentritugally :responsive -;e1ement lot theoentenof wgravity thereof-mime forcegaotp ing upon the resilient moonsfrom the axi-s of ;-ro,tation of the rotatable member radially ouWarclly from said letter i axis, I and means responslVe :to a variationbetween the lfOtatiOIlfl-l vspeeds of the propeller androtatablemembersafor Naming the pitch of the propeller qblades vto bring therotetionel speed of the propeller ,hackltoward th rotational speed ofthe rotatable @member.

11. Mechanism of the glass described, .comprising, in icombination,propeller supporting means, a propeller therefor mounted for rota tionthereon, "a rotatable ,member mounted on said supportingmeans forrotation independently of said propeller, a oentrifugally responsive e16ment corried by id rotatablermemberr-for 111. 3% ,men r dially the of,re lient rmeans yieldabl opp s n radial outward movement f said 1e1 mert, means to rotate said rotatable ,member :fl-I .& rotational speedgvvhioh is a function of -;the speed of bodily travel of said supportingmeans, said \oentrifngally {responsive element oooperating with vsaidrotation means to vnry the torque vforce applied ther by to rotate theJ'Qtatahke membernpon radial movement of "said centrifiugal element,said resilient means bein 2stressed hy cooperation with said;centrifueel element at the leenter of ravity thereof with .a :fomonotin l pon the resilient means from the axis of "rota- ,tion of vtherotatable member raicliall-y outwardly therefrom, :and me ns nespons veto ;a variation between the rotational speeds of the propeller vandrotatable :member {for varying the rotational speed ,of the :propellerto bring the rotational spe d of h oronelle hack toward the rotationalspeed of the'r otettnble member, combined with :a. centrifu al brakeelement carri d by said propeller for radial movement relative heretoand cooperating with the rotatable member to lock the some tothepropellerjorrotatlon therewith, resilient moons ielnablvopposingradieloutwarol movement of said brake element, saidvbra ke e ement andsaid resilient means being calibrated to permit radialoutwardmovernentpof theibragke element for releasing the locked relationat a predetermined --rotational speed of the propeller.

l2. Mechanism of the class described, comprising, in combination,propellersupporting-means, a propeller therefor mounted :for rotationt-hereton, 'a rotatable member -mounted .on said supp t n means zforrotation independentl for said =prope11er, a oentlriiileelly responsiveelement hen ried by said rotatable member for .tnovomont radiallythereof, :resili ent means yieldahly 2 1 n sin r dial ou warrl .m vemenof said elem nt, vm ons to rotat said ro atable member at a rotationalspeed wh-ich is a function of the speed of bodily travel of saidsupporting means, said centrifugally responsive element cooperating withsaid rotation means to vary the torque force applied thereby to rotatethe rotatable member upon radial movement of said centrifugal element,said resilient means being stressed by cooperation with said centrifugalelement at the center of gravity thereof with a force acting upon theresilient means from the axis of rotation of the rotatable memberradially outwardly therefrom, and means responsive to a variationbetween the rotational speeds of the propeller and rotatable member forvarying the rotational speed of the propeller to bring the rotationalspeed of the propeller back toward the rotational speed of the rotatablemember, wherein the last means includes a shaft carried by the propellerfor rotation therewith and also independently thereof, said shaft b6i1=gconnected with said rotatable member for rotation thereby relatively tothe propeller upon a variation between the rotational speeds of thepropeller and said rotatable member, a driving member yieldablyconnected with said shaft for rotation therewith up to a predeterminedloading and for rotation relative to said shaft when the resistance torotation thereof exceeds said loading, andmeans interconnecting saiddriving member with said propeller blades for varying the pitch thereofupon rotation of said driving member.

13. Mechanism of the class described, comprising, in combination,propeller supporting means, a propeller therefor mounted for rotationthereon, a rotatable member mounted on said supporting means forrotation independently of said propeller, a centrifugally responsiveelement carried by said rotatable member for movement radially thereof,resilient means yieldably opposing radial outward movement of saidelement, means to rotate said rotatable member at a rotational speedwhich is a function of the speed of bodily travel of said supportingmeans, said centrifugally responsive element cooperating with saidrotation means to vary the torque forceapplied thereby to rotate therotatable member upon radial movement of said centrifugal element, saidresilient means being stressed by cooperation with said centrifugalelement at the center of gravity thereof with a force acting upon theresilient means from the axis of rotation of the rotatable memberradially outwardly therefrom, and means responsive to a variationbetween the rotational speeds of the propeller and rotatable member forvarying the rotational speed of the propeller to bring the rotationalspeed of the propeller back toward the rotational speed of the rotatablemember wherein the last means includes a shaft carried by the propellerforv rotation therewith and also independently thereof, said rotatablemember being rotatably mounted on said shaft for limited axial shiftingmovement relative thereto upon rotation of said rotatable memberrelative to said shaft and for rotation of said shaft with saidrotatable memher at the limits of axial shifting movement, a centrifugalbrake element carried by said propeller-for radial movement relativethereto and engageable with the rotatable member to lock the same to thepropeller when the rotatable member is at one limit of axial shiftingmovement, and a rotatable'element carried by said rotatable member forrotation relativethereto and enga'geable with the centrifugal brakeelement when the rotatable member is at its other limit of axialshifting movement.

14. Mechanism of the class described, comprising, in combination, apropeller having variable pitch propeller blades, a centrifugallyresponsive weight element for each blade and arranged for movementradially of the propeller axis and cooperable with its blade to vary thepitch thereof upon radial movement of said element, and resilient meansyieldably opposing radial movement of said elements, said resilientmeans being stressed by cooperation with said elements at the center ofgravity of the latter with a force acting upon resilient means from theaxis of rotation of the propeller radially outwardly from said latteraxis, said resilient means and said elements being arranged so that thradius of rotation of the latter is the distance which the resilientmeans is stressed to produce the force opposing radial outward movementof said element.

a 15. Mechanism of the class described, comprising, in combination,propeller supporting means, a propeller therefor mounted for rotationthereon, a rotatable member mounted on said supporting means forrotation independently of said propeller, a centrifugally responsiveelement carried by said rotatable member for movement radially thereof,resilient means yieldably opposing radial outward movement of saidelement, means to rotate said rotatable member at a rotational speedwhich is a function of the speed of bodily travel of said supportingmeans, said centrifugally responsive element cooperating with saidrotation means to vary the torque force applied thereby to rotate therotatable member upon radial movement of said centrifugal element, saidresilient means being stressed by cooperation with said centrifugalelement at the center of gravity thereof with a force aotingupon theresilient means from the axis of rotation of the rotatable memberradially outwardly therefrom, and means responsive to a variationbetween the rotational speeds of the propeller and rotatable member forvarying the rotational speed of the propeller to bring the rotationalspeed of the propeller back toward the rotational speed of the rotatablemember, wherein the last means includes a shaft carried by the propellerfor rotation therewith and also independently thereof, said rotatablemember being rotatably mounted on said shaft for limited axial shiftingmovement relative thereto upon rotation of said rotatable memberrelative to said shaft and for rotation of said shaft with saidrotatable member. at the limits of axial shifting movement, acentrifugal brake element carried by said propeller for-radial movementrelative thereto and engageable with the rotatable member to lock thesame to the propeller when the rotatable member is at one limit of axialshifting movement, anda rotatable element carried by said rotatablemember for rotation relative thereto and engageable with the centrifugalbrake element when the rotatable member is at its other limit of axialshifting movement, a driving member yieldably connected'with said shaftfor rotation therewith up to a predetermined loadingand for rotationrelative to said shaft when the resistance to rotation thereof exceedssaid loading, and means interconnecting said driving member with saidpropeller blades for varying the pitch thereof upon rotation of saiddriving member.

16. Mechanism of the class described, com-

